Cap tightener



FIG. 1 is a bottom perspective view of an exemplary cap tightener;

FIG. 2 is a top perspective view thereof;

FIG. 3 is a top plan view thereof,

FIG. 4 is a bottom plan view thereof;

FIG. 5 is a front elevation view thereof; and,

FIG. 6 is a front left elevation view thereof. 

CLAIM The ornamental design for a cap tightener, as shown and described. 